Method of obtaining phenyl-azo-alpha-alpha-diamino-pyridine hydrochlorides



Patented June 9, 1 931 UNITED s-r Tss I'WAN oscrnoivrrsiunnsKY, or NEWYORK, n. Y nssrenon TO THE VPYRIIZDFIUIVI con- I ronnrroiv, on NEW YORK,n. Y.,

A CORPORATION OF NEW YORK "METHOD or OBTAININGPI-IENYL-AZO-ALPH.A-ALZPH,A-DIAMINO-PYRID1NE HYDRO? I oHLoRInEsi NoDrawing. Original application filed September'23, 1927, Serial No.221,629. Divided and use application filed May 31, 1928. Serial No.282,052.

This invention is an improvement in methods of obtainingphenyl-azo-alpha-alpha-diamino-pyridine hydrochlorides, and theapplication is a division of Patent No.

5 1,680,111, granted August 7th, 1928.

.Contrary to former beliefs as for instance, that of Cliichibabin'enunciated in hisbook Investigations in Pyridine Bases, 1918, Moscow-,Ihave discovered that phenyl-azo- 1O alpha-alpha-diamino-pyridinefunctions not only as a mono acid but likewise as a diacid base.Chemically pure phenyl-azo-alpha-alpha-diamino-pyridine dihydrochloride,whichI succeeded in isolating, comes in the 1 form of beautiful smallprisms, dark red in color with a violet tinge, and which shimmer. Underthe action even of cold water'these compounds split off one molecule ofhydrochloric acid and are transformed tophenylazo-alpha-alpha-diamino-pyridine monohydrochloride. i

Probably it was precisely this hydrolysis which occurs in thedihydrochloride of this substance, that prevented Chichibabin fromseparating off analogous compounds. In washing t-he various compounds hehad obtained with water, Chichibabin decomposed the di-salts and wasthus unable to discover the existence of these salts. As concentratedand even 6% hydrochloric acid does not decompose dihydrochloride, thiscompound is easily produced by means of simple copulation of diazotizedaniline. with alpha-alpha- .diamino-pyridine, of course provided thesolutions of these substances be sufficiently concentrated and contain asuflicient amount of hydrochloric acid (not less'than' 6%).

from almost amorphous micro-crystalline mono-hydrochloride in, powderform, whichdisplays colloidal prop erties, it is easily and very'rapidlyfiltered under pressure and is likewise very easily separated off fromits mother liquor on a centrifuge; the residue which it has absorbedbeing easilyv removedby Washing thesubstance in a weak, say 10%,solution of hydrochloric acid. The phenyl-azo-alpha-alphadiamino-pyridinemonohydrochloride, may be obtained by pouring distilledwater at room temperature over a dihydrochloride after it has beenpurified in the above described way. 7 In this process thedihydrochloride immediately: and quantitatively splits off one moleculeofhya drochloric acid and is thus convertedto chemically'puremonohydrochloride. The latter I substance is then separated off eitherby cen-'" PATENT; OFFICE from cold water, which entails considerableloss of the substance.

. sample I V 5191.28 gms. of freshly-distilled aniline are dissolved ina mixture of 14 litres of 37% hydrochloricacid and 2a litres ofdistilled water; About 10 kilograms ofice must then be added to thesolution. The diazotization' process is conducted by means of a solutionof 3798 gms. of sodium nitritein 30 litres of water at 12 C.,approximately. Of course the process is checked with iodostarclr paper.hen the diazotization is completed 1 a solution of 6000 gms. ofalpha-alpha-diamino-pyridine in 30 litres of 20% hydrochloric acid isadded at one time into the product obtained. i v l I found by experiencethat the'temperatu're of the freshly-prepared mixture should not beallowed to fall below 12 C. However, the j if 1 most favorabletemperature forthis reaction is 1618 C. Only .at this relatively hightemperature after diazotization'does the mixture, when it has beenallowed to stand for some 30-120 minutes, give a copious sediment ofphenyl-azo-alphaalpha-diannno-pyridme dihydrochloride, it precipitatesrapidly to,

Properties 0 7 the dihydrochloride As distin uished from the mono-hydrochloride, the substance which is obtained in the above described way,dissolves in cold aniline or pyridine. The solutions are from orangeyellow to deep red in color, depending on the concentration.Phenyl-azdalphaalpha diaminopyridine dihydrochloride is soluble ineither aniline or pyridine contrary to phenyl-azo-alpha-alpha-diamino-pyridinehydrochloride, which only very slightly soluble. Mostlikely these solutions contain free phenyl-azo-alpha-alpha-diainino-pyrhdine-mOno-hydrochloride and aniline and pyridine hydrochloriderespectively. This substance dissolves easily in methyl and ethylalcohol; in benzene and anhydrous acetone it is almost insoluble; whenboiled with benzol (83 ,C.) it retains both its crystalline form andits-glitter. In contradistinction to the monohydrochloride, thedihydrochloride dissolves very rapidly in lulre-warin water. But even ifcold water is poured over it, it immediately loses its glitter andcrystalline'form, and is converted to mono-hydrochloride. Asdistinguished from the aqueous solutions of the monohydrochloride thedihydrochloride solutions show a distinct acid reaction to congo paper.

Under the action of ammonia, dihydrochloride in powder form immediatelychanges its violet red color to a golden yellow and is transformed to fre phenyl-azo-diainino-pyridines which melt at 139 C. after a triplerecrystallization from boiling water.

Concentrated and even 6% hydrochloric acid does not produce any actionon dihydrochloride, but it decomposes partially under the action of lr") hydrochloric acid, forming the"mono-hydrochloride. A part of theoriginal crystals remain unchanged in this reaction. 3% hydrochloricacid decomposes dihydrochloride to the mono-hydrochloride and freehydrochloric acid. The reaction takes place gradually butquantitatively. It takes three days to be completed. If heated in a testtube in an oil bath, chemically pure dihydrochloride at 1802lO 'C.splits off one molecule of hydrochloric acid and is converted to themono-hydrochloride.- In this reaction the original dihydrochloridecrystal lose their glitter and become dull, although retaining theiroriginal shape. The resulting product yields perfectly neutral solutionswith boiling water.

In this heating process (BO-210 C.) dihydrochloride splits off its waterof recrystallization which can be collected in a container and theamount of hydrochloric acid split off can be ascertained by means ofsilver-nitrate. Under the same conditions phenyl-azo alphadiaminopyridine hydrochloride (180210 C.) gives no water at all andsplits 05 only a negligible quantity of hydrogen chloride in traces. Ifheated in a capillary tube dihydrochloride begins to split onhydrochloric acid perceptibly only at 180 C. The complete decompositionand coagulation temperatures for both compounds (i. e.mono-and-di-hydrochloride) in the process of heating in a capillarytube, lie around 220-22 l C.

As has already been mentioned in the text of the present appplicationthe new compound which I separated ofi facilitates and reduces the costof the process of obtaining mono-hydrochlorides, as already described byme, to quite a considerable extent A closer investigation of thephenyl-azoalpha-alpha diaininopyridine obtained by conversion of thedihydrochloride into monohydrochloride as described in Example I shows,that whilst being but sli htly toxic it displays very strongbactericidal properties. It dissolves quite easily in boiling water andthe 1 to 2.5% aqueous supersaturated solutions made with it displayconsiderable stability.

The behaviorof aniline homologues and analogues, such as phenetidine,anisidine, toluidine, in copulation with alpha-alphadiamino-pyridine isanalogous with that of aniline itself. I have observed that under thesame conditions these amines produce the dihydrochloride of thecorresponding arylazo-alpha-alpha-diamino-pyridines. In turn thesedihydrochlorides are converted by treatment with water to thecorresponding mono-hydrochlorides.

The dihydrochloride of phenyl-azo-alphaalpha diamino-pyridine asdescribed in this application, and the existence of which could not beforetold a priori, presents a certain interest for the followingreasons 1. By means of the given dihydrochloride, the monohydrochlorideof phenyl-azo-alphaalpha-diamino-pyridine, in chemically pure condition,may be easily and quickly obtained from aniline and diamino-pyridine, ashas already been pointed out. I r

2. In reaction with distill-ed water, the

.dihydrochlori'de of phenyl-azo-alpha-alphadiamino-pyridine instantlysplits off one molecule of hydrochloric acid and is thereby convertedinto. monohydrochloride of phenyl azo alpha alpha diamino pyridine. Thephenyl azo alpha alpha --dia1ninopyridine hydrochloride so produced isdistinguished from phenyl-azo-alpha-alpha-diamino-pyridine hydrochlorideobtained in the ordinary way, in that it dissolves relatively w moreeasily in cold water. Inthis way it becomes possible to obtain verystrong and probably supersaturated solutions ofphenylazo-alpha-alpha-diaminopyridine hydrochloride, say 3% solutions,which are fairly stable, whereas, strong solutions ofphenylazo-alpha-alpha-diaminopyridine hydrochloride (3%) obtainedwithout the aid of dil hydrochloride are distinguished by their notintended as limitations.

The chemical reactions described, are illustrated in the accompanyingstructural formulas.

. +CI.N:NO {INN-O HZN N NH: H01 H01 What is claimed as new is The methodof obtaining dihydrochlori'de ofphenyl-azo-alpha-alpha-diamino-pyridine,

which consists in copulation of phenyldiazonium-chloride withdiamino-pyridine in a medium containing not less than 8% (by weight)hydrochloric acid.

Signed at New York city, in the county of v New York and State of NewYork, this 25th day of May, A. D. 1928. TWAN OSTROMISLENSKY.

